Antimicrobial adhesive composition with copper nanoparticles for dentures

ABSTRACT

The present invention concerns a new antimicrobial denture adhesive composition useful to be used for fixing dentures, which includes copper nanoparticles (CuNPs) that provides antimicrobial properties against dental pathogens such as  Candida albicans, Streptococcus mutans, Staphylococcus aureus  and  Aggregatibacter actinomycetemcomitans . Surprisingly, the composition for a denture adhesive comprising copper nanoparticles (CuNPs) not only shown excellent antimicrobial properties, but also improved adhesive properties in comparison with other denture adhesives existing currently in the marked, which do not contain said CuNPs.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional-in-part application of the U.S. Ser.No. 16/067,053 application, filed on Jun. 28, 2018, which is a nationalstage application of International Application PCT/CL2016/050079, filedon Dec. 29, 2016, which claims priority to Chilean Application3781-2015, filed Dec. 30, 2015, the disclosure of each of which isincorporated by reference their its entirety herein.

FIELD OF THE INVENTION

The present invention relates to an adhesive composition, to be used forfixing dentures, which includes copper nanoparticles (CuNPs) thatprovides antimicrobial properties against dental pathogens such asCandida albicans, Streptococcus mutans, Staphylococcus aureus andAggregatibacter actinomycetemcomitans. The invention also relates withthe method for obtaining said composition and the use of the compositionagainst the oral pathogens Candida albicans, which causes subprostheticstomatitis, Streptococcus mutans, responsible for caries formation,Staphylococcus aureus, which causes periprosthetic infections andAggregatibacter actinomycetemcomitans, which causes gingivitis.

BACKGROUND OF THE INVENTION

The use of dental prostheses continues to be the most widely used dentalrehabilitation solution, particularly in the lower socioeconomic strata.Prosthetic cleaning is essential to maintaining good oral hygiene and toprevent Subprosthetic Stomatitis, a chronic inflammation of the oralmucosa that is in contact with the prosthesis. Despite the fact that itsetiology remains undefined, its main cause is linked to fungalinfections. Since the vast majority prosthesis users are elderlyseniors, cleaning habits are often poor, in part due to the visual andpsychomotor limitations of this patient group. The current treatment forthis type of infection is via oral and topical anti-fungal agents;however, these agents can lead to undesirable side effects for patients,such as general discomfort and a particularly unpleasant taste.

Patients who use removable dental prostheses often resort to the use ofadhesives that improve the retention and fit of their prosthesis, whichgives it an improved chewing function, as well as greater psychologicalsafety, comfort, and confidence. The substances that make up theadhesive, when mixed with saliva, generate retentive forces that fix theprosthesis to the oral mucosa. Despite the important benefits thatdentures adhesives provide, their use also favors the accumulation andproliferation of microorganisms. Especially fungi (yeasts) of the genusCandida responsible for producing sub-prosthetic stomatitis and angularcheilitis, oral infections highly prevalent in dentures users.Stomatitis is characterized by causing redness, inflammation, irritationand pain on the palate and gums of patients. For this reason, it isnecessary to develop more advanced prosthetic adhesives that can reducethe proliferation of yeasts such as Candida albicans in patients who usethis type of product.

It is well known the antimicrobial properties of metals, that's why theyare currently being studied for use in many applications with the helpof nanotechnology, such as surface disinfection and topical applicationin gels and pastes. Copper, which has been widely used in medicine sincethe 19th century, was indicated in the treatment of skin infections,lupus, and was even used as an antimicrobial agent until the appearanceof antibiotics in 1932 (Grass, G., C. Rensing, and M. Solioz, MetallicCopper as an Antimicrobial Surface. Applied and EnvironmentalMicrobiology, 2011. 77(5): p. 1541-1547). Copper has been used fordecades for its antifungal properties (Cioffi, N., Torsi, L.,Ditarantano, N., Tantalillo, G., Ghibelli, L., Sabbatini, L.,Bleve-Zacheo, T., D'Alessio, M., Zambonin, P G., Traversa, E., Coppernanoparticle/polymer composites with antifungal and bacteriostaticproperties. Chem. Mater, 2005, 17, 5255-5262; and Palza, H., Quijada,R., Delgado, K, Antimicrobial polymer composites with copper micro- andnanoparticles: Effect of particle size and polymer matrix. Journal ofBioactive and compatible polymers. 2015, 1-15).

Copper is an active agent in toothpaste formulations with microbialplaque control properties. Thus, document U.S. Pat. No. 4,332,791describes a toothpaste containing silica and copper salt (0.001-5%) asactive components, whereas in document EP 0471396 A1, the activeingredient consists of a copper salt (0.01-5%), sodium bicarbonate andan alkylamine that acts as a stabilizer of the metal ion. Salts such ascopper salicylate (0.05-0.3%) have also been used in the formulation ofmouthwashes for the control of oral ulcers and irritations, as describedin document US 2011/0229534 A1.

In particular, for adhesive compositions, document EP 1003791 A4 relatesto the use of copper for the control of subcutaneous stomatitis anddescribes a formulation of an antimicrobial adhesive cream for dentalprostheses, in which the active ingredient of the adhesive consists of8-hydroxyquinoline (0.0001-0.5%) and a copper salt II (0.001-0.3%),which shown greater activity against C. albicans in in-vitro tests.

Besides, document U.S. Pat. No. 7,008,976B2 relates to a dentureadhesive composition comprising mixed salts of an alkyl vinylether-maleic acid or anhydride copolymer and/or terpolymer withisobutylene, wherein the mixed salt contains a cationic salt functioncomprising at least about 1% strontium cations, from about 1% to about40% of zinc cations, from 0% to about 2.5% of a cation selected from thegroup consisting of iron, boron, aluminum, vanadium, chromium,manganese, nickel, copper, yttrium, titanium, and mixtures thereof; fromabout 36% to about 60% free acid component; and from 0% to about 65% ofa cation selected from the group consisting of magnesium, calcium, andmixtures thereof. The invention also includes a method of increasing theadhesion of dentures to the oral cavity by applying the abovecompositions to dentures, directly to the oral cavity, palate or ridgeof the oral cavity, or applying it to both, and thereafter securing thedentures to the ridge or palate of the oral cavity.

On the other hand, better antimicrobial properties have been observed incopper nanoparticle form when compared to micro size (Theivasanthi, T.,Studies of Copper Nanoparticles Effects on Micro-organisms. Annals ofBiological Research, 2011. 2(3): p. 368-373). It has also been aneffective killer of numerous strains of hospital-acquired infections,although there is a need for controlled release of ions into the localenvironment to achieve optimal antimicrobial activity (Ren, G., et al.,Characterisation of copper oxide nanoparticles for antimicrobialapplications. International Journal of Antimicrobial Agents, 2009.33(6): p. 587-590). The antimicrobial properties of CuNPs have so farbeen assessed against the bacteria Escherichia coli, Staphylococcusaureus, Klebsiella pneunomiae, Lysteria monocytogenes and Pseudomonasaeruginosa, as well as against Saccharomyces cerevisiae yeast. However,the prior art shows no evidence regarding its effect on oral bacteria.

Research on the bactericidal mechanism of copper as a nanoparticle showsthat the effect is largely due to its small size and large contactsurface, in relation to its volume, which allows for easy interactionwith microbial membranes. (Chatterjee A K, Ruchira C, Tarakdas B.Mechanism of antibacterial activity of copper nanoparticles.Nanotechnology. 2014; 25(13):135101).

The antimicrobial capacity of these particles has led to exploring thepossibility of incorporating copper nanoparticles into adhesivecompositions that are used in those people in need of dentures.

Our present aim is to contribute with the oral hygiene by providing anadhesive composition to be used with dentures, which shows antimicrobialproperties. This adhesive contains, as main ingredient, coppernanoparticles (CuNPs). As far as we know, there are no denture adhesivescontaining copper nanoparticles (CuNPs) as active component.

SUMMARY OF THE INVENTION

In one embodiment the present invention relates to an antimicrobialdenture adhesive composition, wherein the composition comprises:

-   -   a cellulose polymer or its derivatives;    -   a copolymer of methyl vinyl ether and maleic anhydride (PVM/MA)        or it derivatives;    -   copper nanoparticles (CuNPs); and    -   a hydrophobic vehicle.

In one preferred embodiment of the present invention, the antimicrobialdenture adhesive composition comprises:

-   -   mineral oil between 20.0 to 30.0 w/w %;    -   petrolatum between 25.0 to 35.0 w/w %;    -   copolymer of methyl vinyl ether and maleic anhydride (PVM/MA)        between 28.0 to 37.0 w/w %;    -   carboxymethylcellulose between 14.0 to 23.0 w/w %; and copper        nanoparticles (CuNPs) between 0.030-0.100 w/w %.

In another preferred embodiment of the invention the coppernanoparticles (CuNPs) of the antimicrobial denture adhesive compositionhave dimensions of 5 to 200 nm and they have a morphology selected fromthe group consisting spherical, tubular, cubic fibrous, wire, laminarmorphology and any other morphology having at least one of itsdimensions in nanometric scale.

In another yet preferred embodiment of the present invention said coppernanoparticles (CuNPs) contain copper having an oxidation number of 0, 1,2 or one intermediate oxidation state, so the nanoparticles could bemade of Cu, Cu₂O or CuO. In another yet preferred embodiment of thepresent invention said copper nanoparticles (CuNPs) has a structure ofcopper supported on ceramic nanoparticles selected from the groupconsisting in silica, clay, zeolite, titanium and zirconium oxides.

In a second embodiment of the present invention, it relates with saidantimicrobial denture adhesive composition which is obtained by a methodcomprising the following main steps:

-   -   (i) adding between 20.0 to 30.0 w/w % of mineral oil and between        25.0 to 35.0 w/w % of petrolatum and mixing them at 60° C. under        a stirring speed of 200-300 for 10 minutes;    -   (ii) adding copper nanoparticles (CuNPs) to the former mixture        and stirring he resulting mixture for at 60° C. for 10 minutes;    -   (iii) adding copolymer of methyl vinyl ether and maleic        anhydride (PVM/MA) between 28.0 to 37.0 w/w % and        carboxymethylcellulose between 14.0 to 23.0 w/w % and stirring        the resulting mixture for 40 minutes at 60° C.; and    -   (iv) allowing the obtained product to cool at room temperature.

In a third embodiment of the present invention, it relates with the useof the antimicrobial denture adhesive composition based on coppernanoparticles (CuNPs) which is useful against the oral pathogens C.albicans, which causes subprosthetic stomatitis; Streptococcus mutans,responsible for caries formation; and Staphylococcus aureus, whichcauses periprosthetic infections.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR)spectroscopy spectrum of the Corega® denture adhesive compared to apreferred formulation of the denture adhesive composition containingcopper nanoparticles (CuNPs) of the invention.

FIG. 2 Compositional analysis of the preferred formulation of thedenture adhesive composition containing copper nanoparticles (CuNPs)performed by Energy Dispersive X-Ray Analysis (EDX) coupled to ScanningElectron Microscopy (SEM).

FIG. 3. Shows antibiograms of the Corega® prosthesis adhesive comparedto a preferred formulation of the prosthesis adhesive compositioncontaining copper nanoparticles (CuNPs) of the invention against theCandida albicans fungus.

FIG. 4. Shows the adhesive strengths of two commercial prosthesisadhesives compared to the prosthesis adhesive composition containingcopper nanoparticles (CuNPs) of the invention measured by mechanicaltensile tests.

DETAILED DESCRIPTION OF THE INVENTION

The present invention focuses on the development of a new compositionfor a denture adhesive with antimicrobial properties to be used infixing dentures in people in need of it.

Surprisingly, the composition for a denture adhesive comprising coppernanoparticles (CuNPs) not only shown excellent antimicrobial properties,but also improved adhesive properties in comparison with another dentureadhesives existing currently in the marked, which do not contain saidCuNPs.

The denture adhesive composition of the invention comprises also anhydrophobic carrier or vehicle selected from petrolatum or petrolatumcombined with mineral oil, natural wax, synthetic wax, polyvinylacetate, natural oils, synthetic oils, fats, silicone, siliconederivatives, dimethicone, silicone resins, hydrocarbons, hydrocarbonderivatives, essential oils, caprilic/capric triglycerides, polybutene,oleic acid, stearic acid, and combinations thereof; and a polymermaterial derivated from cellulose selected from hydroxypropylmethylcellulose, carboxymethyl-cellulose, hydroxyethylcellulose,hydroxypropylcellulose, hydroxyethylmethylcellulose,hydroxyethylmethylcellulose, methyl-cellulose, methylcarboxymethylcellulose, hydroxyethylcarboxymethyl cellulose,hydroxyethylmethylcarboxy methylcellulose, sulfoethylcarboxymethylcellulose, hydroxyethylhydroxypropyl cellulose, hydroxyethylethylcellulose, hydroxyethylsulfoethyl cellulose or combinations thereof.

In a preferred embodiment, the polymer material derivate from celluloseis carboxymethyl-cellulose.

The invention further comprises a polymer material selected frompoly(methylvinyl ether-co-maleic acid) (PVM/MA) and its derivatives,such as acids, salts or anhydride.

In addition to the above-mentioned components, the present compositionmay optionally contain other components to improve or enhance theadhesive nature of the base components, including those commonly knownand used by the denture adhesive industry. Examples include but are notlimited to dicalcium phosphate and nanoclay.

The dental adhesive composition of the invention may comprise additionalcomponents, such as plasticizers, rheology modifiers, preservatives,humectants, emulsifiers, antioxidants, super-disintegrants orabsorbents, flavoring agents, colorants, cross-linking agents,non-metallic antimicrobial agents, control release agents, antifoamingagents, sweetening agents and viscosity modifiers.

EXAMPLES 1. Example 1 Obtaining CuNPs

Copper nanoparticles (CuNPs) can be obtained using well knowntechnologies (Madhulika Bhagat et. al., Review—Multifunctional CopperNanoparticles: Synthesis and Applications, ECS Journal of Solid StateScience and Technology, 2021, 10, 063011).

Alternatively, enveloped CuNPS in ceramic material particles can beprepared. For that, zeolite particles (nanoporous crystallinealuminosilicate) and silica nanoparticles were used as supportmaterials, using natural zeolite of national origin (MOR) and commercial100 nm silica nanoparticles. CuNPs are formed on site in the material,whereby a certain MOR mass was contacted with a 0.1 M copper acetatesolution for 24 h at room temperature. Once the ion exchange period wascompleted, the zeolite was separated and washed by repeatedcentrifugation/dispersion cycles. The resulting material was thendispersed in a starch/ascorbic acid reducing solution and microwaved fora few seconds.

This system for the formation of CuNPs in biopolymers was developed byour laboratory team under the concept of “Green Chemistry”, with the aimof synthesizing more benign metallic nanoparticles that are compatiblewith biomedical applications. The CuNPs/MOR particles were separated,washed and dried for further use in the preparation of the antimicrobialdenture adhesive composition.

2. Example 2 Preparation of the Antimicrobial Denture AdhesiveComposition Containing CuNPs

25 g of mineral oil (w/w) and 28.4 g of petrolatum (w/w) are mixed at60° C. under a stirring speed of 300 ppm for 10 minutes. Next, 0.071 gof copper nanoparticles (w/w) are added and the mixture is stirred atthe same temperature for 10 minutes. Next, 31.6 g of PVM/MA (w/w) and14.9 g of carboxymethylcellulose are added (w/w), and the resultingmixture is stirred for 40 minutes at 60° C. The product obtained isallowed to cool to room temperature.

In order to compare the chemical structure of the antimicrobial denturecomposition with CuNPs with known denture adhesives in the market,adhesives were analyzed by using total attenuated reflectance withFourier transform infrared spectroscopy (ATR-FTIR) in an Agilent Cary630 ATR-FTIR spectrometer.

FIG. 1 shows the results of said ATR-FTIR analysis, which evidences thatthe denture adhesive modified with CuNPs have the same spectrum thanthat of Corega®, so the presence of CuNPs does not alter the structureof the denture adhesive.

Additionally, the adhesive elemental composition was analyzed by X-raydispersive energy spectroscopy (EDX) coupled to scanning electronmicroscopy (SEM) in a JEOL model JSMIT300LV microscope. FIG. 2 showsCopper EDX elemental mapping of the denture adhesive formulated withCuNPs, which confirms the incorporation of CuNPs in the PVM/MA adhesivematrix.

3. Example 3 In-Vitro Assessment of the Antimicrobial Properties of theAntimicrobial denture adhesive composition containing CuNPs

Antimicrobial properties of the denture adhesives were assessed againstCandida albicans, pathogen responsible of denture stomatitis disease, byusing the agar disk-diffusion method. Filter paper discs of 6 mm indiameter were impregned with the denture adhesives for 20 minutes. Afterthat, 100 μL of 0.5 Mcfarland (1-5×106 CFU/ml) of ATCC 90029 strain ofCandida albicans were seeded on plates of Sabouraud dextrose agarmedium. Then, adhesive—impregnated disks were placed onto the surface ofthe inoculated agar plate. Each disk was pressed down to ensure completecontact with the agar surface, and they were distributed evenly so thatthey were no closer than 24 mm from center to center. The plates wereincubated at 37° C. under aerobic conditions for 48 hours after whichthe disks were applied. Plates were examined after 48 h of incubation(FIG. 3). The diameters of the resulting zones of inhibition weremeasured to the nearest whole millimeter at the point at which there wasa prominent reduction in growth.

4. Example 4 Determination of the Improved Adhesive Properties of theAntimicrobial Denture Adhesive Composition Containing CuNPs

Adhesive properties were measured by using mechanical tensile tests in aDEBEN microtest machine (Suffolk, UK) using a 2 N load cell. Dentureadhesives were applied on the surface of two dental acrylic specimenshaving a flat area of 60 mm² and perpendicular to the long axis. The twoacrylics were bonded and immersed in artificial saliva for 5 minutes toensure adhesion between opposing acrylic specimens. After that, thespecimens were debonded in tensile mode at a rate of 1 mm per minute byusing the microtest machine. The maximum force before failure was thencalculated (adhesive resistance).

The presence of CuNPs in the adhesive also gives it improved adhesiveproperties (FIG. 4).

The tensile mechanical properties of the adhesive formulated with CuNPsare shown compared to other commercially available prosthetic adhesives.The adhesive strength of denture adhesive with CuNPs was statisticallyhigher than that of two of the more well-known commercial adhesivescurrently in the market. These results demonstrate that CuNPs alsoproduce a mechanical reinforcement of the adhesive which provokesgreater fixation and stability of dental prostheses in users.

Advantages of the Present Invention

The antimicrobial denture adhesive composition containing CuNPs has beenvalidated in its antimicrobial and adhesive properties. It has beenobtained an optimized formulation that maximizes its antimicrobial andmechanical properties.

The scaling steps of the said adhesive composition making process werecompleted in a cosmetic/pharmaceutical/dental industrial plant.Likewise, a pilot of the packaging process of the new adhesive wascarried out.

A product satisfaction and validation study is currently being carriedout in a population of 30 patients compared to the conventional Corega®adhesive.

1. Antimicrobial denture adhesive composition, comprising: a cellulosepolymer or its derivative; a copolymer of methyl vinyl ether and maleicanhydride (PVM/MA) or their derivatives; copper nanoparticles (CuNPs);and a hydrophobic vehicle.
 2. Antimicrobial denture adhesive compositionaccording to claim 1, comprising: mineral oil between 20.0 to 30.0 w/w%; petrolatum between 25.0 to 35.0 w/w %: copolymer of methyl vinylether and maleic anhydride (PVM/MA) between 28.0 to 37.0 w/w %;carboxymethylcellulose between 14.0 to 23.0 ; and copper nanoparticles(CuNPs) between 0.030-0.100 w/w %.
 3. Antimicrobial denture adhesivecomposition according to claim 1, wherein copper nanoparticles (CuNPs)have dimensions of 5 to 200 nm.
 4. Antimicrobial denture adhesivecomposition according to claim 1, wherein copper nanoparticles (CuNPs)have a morphology selected from the group consisting in spherical,tubular, cubic, fibrous, wire, laminar and any other morphology havingat least one of its dimensions in nanometric scale.
 5. Antimicrobialdenture adhesive composition according to claim 1, wherein said coppernanoparticles (CuNPs) contain copper having an oxidation number of 0, 1,2 or one intermediate oxidation state.
 6. Antimicrobial denture adhesivecomposition according to claim 1, wherein said copper nanoparticles(CuNPs) has a structure of copper supported on ceramic nanoparticlesselected from the group consisting in silica, clay, zeolite, titaniumand zirconium oxides.